dumbwaiter

As a noun dumbwaiter

is (obsolete) a table or set of trays on rollers used for serving food.

As a letter x is

the twenty-fourth letter of the.

As a symbol x is

voiceless velar fricative.

As a noun dumbwaiter

is (obsolete) a table or set of trays on rollers used for serving food.

As an adjective undefined is

lacking a definition or value.

As nouns the difference between travelator and dumbwaiter

is that travelator is a moving walkway; a slow conveyor belt that transports people horizontally or on an incline in a similar manner to an escalator while dumbwaiter is a table or set of trays on rollers used for serving food.